The Vostok ice core

The diagram (from Twisted ..) shows the measured CO2 and CH4 concentrations measured from air bubbles trapped in the Vostok ice core, along with temperatures estimated from the isotopic composition of the ice.50

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Temperatures, CO2 concentrations and methane concentrations from the Vostok ice core. The horizontal axes are in years before present. Graphic from Twisted: The Distorted Mathematics of Greenhouse De- nial (figure 27). The vertical scales of the concentration curves are in approximate proportion to the amount of warming expected from each gas in the absence of feedbacks between climate and gas concentrations. These should be taken as indicative — the main uncertainties are in the value of the climate sensitivity used to scale the curves and the global representativeness of the estimated temperatures.